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July 30, 1946.
A. B. KENNEDY
2,405,105
LEACHING APPARATUS AND METHOD
Filed Feb. 24, 1942
2 Sheets-Sheet 1
C(ttomeg
July 30, 1946.
A. B. KENNEDY
2,405,105
LEACHING APPARATUS AND METHOD
Filed Feb. 24, 1942
2 Sheets-Sheet 2
(Ittorneg
Patented July 30, 1946
2,405,105
UNITED STATES PATENT OFFICE
2,405,105
LEACHIN G APPARATUS AND METHOD
Angus B. Kennedy, Chambersburg, Pa.
\ Application February 24, 1942, Serial No. 432,115
9 Claims.
(Cl. 23—310)
1
t)
is!
This invention relates to leaching apparatus,
Still a further object of my present invention
and more particularly to apparatus for extract
ing soluble constituents from solids by the use
of suitable solvents, the present invention being
is to provide, in leaching apparatus of the type
set forth, an arrangement of paddle wheels which
an improvement over that disclosed in my United
States Patent No. 1,628,787.
In this patent, there is disclosed a leaching
apparatus suitable for the extraction of tannin,
dyes, etc., from wood chips, bark root, and other
similar substances. The apparatus comprises, in
general, a tank having a series of adjacent leach~
ing sections through which the material to be
leached is successively passed in one direction
while the solvent is caused to flow therethrough
in the opposite direction, a paddle wheel in each
section being arranged to feed the material
through its own section and into the next succeed
ing section against the ?ow of liquid solvent. In
this way, there is effected a continuous extraction
of the soluble constituents from the solid par
ticles.
More recently, the extraction of oils, fats and
greases from seeds and the like by means of vola
tile solvents, such as hydrocarbon or chlorinated
solvents, has come into fairly general use under
the so-callcd solvent extraction process. Ap
paratus such as that disclosed in my above-iden
ti?ed patent is admirably suited to this process,
although the particular form there disclosed has
several disadvantages from the standpoint of
e?iciency when applied to the extraction of solu~
ble constituents from small particles of solid
matter by means of volatile solvents, and the
primary object of my present invention, therefore,
will insure more uniform power requirements than
was possible with the speci?c form of apparatus
shown in my aforementioned patent.
It is also an object of my present invention to
provide an improved leaching apparatus of the
type described wherein a greater extraction ca
pacity, as well as more uniform extraction, can
be obtained.
A further object of my invention is to provide
an improved leaching apparatus as aforesaid
which is simple, yet sturdy, in construction, highly
efficient in use, and relatively inexpensive to
manufacture.
In accordance with my present invention, I
provide a tank having a plurality of extraction
sections, each provided with its own paddle wheel,
as before, but also provide in advance of the ?rst
extraction section, which is the one into which
the solid material to be leached is admitted, an
additional section which I call the “?lter sec
tion.” This latter section is similar to the other
sections but is provided with a strainer through
which the solvent must pass in leaving the ap
paratus and with a ?lter Wheel similar to the
paddle wheels of the several extraction sections.
I also provide a swinging ba?le plate the pivotal
. mounting of which is over the ?lter section near
the meeting edge of the ?lter section and the
?rst extraction section, and the lower, marginal
portion of which extends into the ?rst extraction
section below the level of the liquid solvent and
is to provide an- improved leaching apparatus 35 carries one or more spacing blocks normally en'
which will be free from the objections to which
gaging the ?rst extraction section at the afore
the speci?c form of apparatus shown in my afore
mentioned meeting edge whereby to leave an
mentioned patent is open.
opening for the ?ow of solvent from the ?rst ex
More particularly, it is an object of my present
traction section to the ?lter section. The swing
invention to provide an improved leaching ap 40 ing bailie plate also carries a scraper which ex
paratus by means of which it will be possible to
tends into the ?lter section and is arranged to
extract with high ef?ciency the desired soluble
< cooperate with the ?lter wheel.
constituents from small particles of solid matter.
The solid material admitted into the ?rst ex
Another object of my present invention is to
traction section through one or more suitable
provide an improved apparatus as aforesaid in
charging spouts contains many particles which
which practically no solid particles, if any, will
are quite ?ne. Now, in the apparatus disclosed
be able to escape the action of the solvent.
in my above-identi?ed patent, it was found that,
till another object of my present invention is
as the material Was fed into the extractor, an
to provide an improved leaching apparatus of the
appreciable quantity of the ?ner, lighter particles
type set forth wherein the trapping and subse
separated from the mass and ?oated on top of
quent advance through the solvent of any par
the solvent in the ?rst extraction section. These
ticles of solid matter which tend to escape at the
particles were carried by the solvent directly
charging section will be assured.
through the perforations of a strainer which
A further object of my present invention is to
originally formed part of the ?rst extraction sec
provide an improved leaching apparatus as set
tion. This separation and carrying away of the
forth above wherein more uniform extraction of
?ner particles not only impaired the extractive
the soluble constituents as the solid material is
efficiency, but also increased the difficulty of
advanced will be possible than was possible with
clarifying the miscella by settling and ?ltering
the speci?c form of apparatus disclosed in my
in a subsequent operation.
above-identi?ed patent.
60
It has been found that when the particles once
2,405,105
3
4
become saturated with the solvent, they tend to
rotation of each wheel). With this arrangement,
agglomerate and remain with the mass; or if they
similar variations in load are encountered by
each of the paddle wheels at the same time with
the result that there occurs a good deal of surg
ing in both the power factor and the extraction
process. According to a further featureof my
become separated from the mass, they agglom
erate and form a sludge which can then be sepa~
rated from the solvent with comparative ease.
Taking advantage of this phenomenon, I provide
the aforementioned swinging baffle to insure that
all particles are carried beneath the surface of
the solvent and are immersed therein. This im
present invention, the paddle wheels are so ar
ranged in their respective sections that the blades
of each succeeding section are displaced angu
' mersion wets the particles and they then tend ll
to agglomerate and remain with the mass. Some
larly somewhat from the corresponding blades
of each preceding section; that is, each paddle
of them, however, will be carried along by the
flowing solvent beneath the baf?e plate into the
?lter section where the proportion of liquid to
wheel is set at a different angle from its pre
ceding paddle Wheel. In this way, the power re
solid is far greater than in the extraction sec
tions, so that the ?ow of solvent in the ?lter sec
traction process is more uniform, and a greater
tion is relatively much slower. Hence, ample
opportunity is afforded to the particles to become
thoroughly saturated with the solvent and to set
tle out in the ?lter section in the form of sludge.
As the ?lter wheel rotates, its blades scrape the
sludge from the bottom of the ?lter section, in
cluding the ?xed strainer therein, the blades also
catching the lighter (or the less saturated) par
ticles which do not settle out as readily. Eventu
ally, each of the ?lter wheel blades, in succession,
engages the scraper on the swinging ba?le plate,
quirements are more evenly distributed, the ex»
capacity is obtained.
The novel features that I consider character
istic of my invention are set forth with particu
larity in the appended claims. The invention it
self, however, both as to its organization and
method of operation, as well as additional objects
and advantages thereof, will best be understood
from the following description of one embodi
ment thereof, when read in connection with the
accompanying drawings, in which
Figure 1 is a longitudinal sectional View of one
form of improved apparatus according to my
thereby forcing the baffle plate to swing for»
present invention,
terial is lost.
At the discharging end of the apparatus shown
Referring more particularly to the drawings,
wherein similar reference characters designate
corresponding parts throughout, there is shown
a tank I provided with a plurality of upwardly
Figure 2 is an enlarged, detail section show
wardly, or up away from the above-mentioned
meeting edge, to thereby expose a relatively large 30 ing the ?rst extraction section, the ?lter section
and the baffle structure associated therewith,
opening into the ?rst extraction section. At the
Figure 3 is a transverse sectional view taken
same time, the scraper scrapes the sludge off
on the line III-III of Figure l, and
from the ?lter wheel blades and causes it to be
Figure 4 is a similar view taken on the line
deposited in the ?rst extraction section through
IV-IV of Figure 1.
this opening. In this way, none of the solid ma
in my aforesaid patent, there is provided a con
veyor which carries away the solid material from
which the soluble constituents have been re
moved, the conveyor passing up at an angle from
a terminal or conveyor section in. which the
concave tubs 3a, 3b, 3c, 3d, 3e, 3)‘, 39, 3h, 32', 39'
which extend across the entire width of the tank
in parallel relation to each other, the tubs being
serially connected to form a continuous leaching
chamber and adjacent tubs meeting along a com
level and into which this liquid is introduced by
mon edge 5. These tubs constitute a plurality of
discharging onto the surface of the liquid. By
successive operating stations or sections at which
this arrangement, the newly introduced solvent
the particles of solid material 1, from which a
has no extractive effect at the time it is intro
soluble constituent is to be extracted by means
duced. In accordance with my present inven
of a ?uid solvent 9, are subjected to the action
tion, however, the solvent is introduced by being
discharged through a perforated spray pipe ex 50 of the ?uid. The tub or section 3a is provided
with a strainer H and constitutes primarily a
tending across the full width of the apparatus
?lter section wherein the ‘?ner, lighter particles
and located at an elevation such that the spray
1 are conditioned to remain in the ?uid, while the
therefrom comes in contact with the solid mate
liquid solvent is maintained at the operating
sections 312,
3:2, 3)‘, 35/, 3h, 32‘, 37' constitute
rial after the latter has been raised above the
level of the liquid in the extractor proper and 55 more particularly extraction sections wherein
the soluble constituent is dissolved out. The
partially drained. Since, with the improved ar
tank I is also provided with a top 2 which may
rangement, the partially drained particles of
be formed with several, preferably covered hand
solid material are sprayed intimately with the
holes or inspection openings l3 and one or more
fresh solvent, a very de?nite, additional extrac
tive effect is obtained thereby and greater ex 60 ventilating pipes l5 through which vapors gen
erated during the leaching process may escape.
tractive efficiency results.
Cooperating, respectively, With the tubs 3a, 3b,
Another feature of the apparatus of my afore
3c, 3d, 3e, 3f, 39, ‘3h, 31', 37' are a plurality of in
mentioned patent which is, under certain cir
dividual paddle wheels 4a, 4b, 4c, 4d, 4e, 4)‘, 49,
cumstances, a disadvantage is the particular ar
rangement of the paddle wheels in the several ex“ 65 4h, 42', 47' each extending across the full width of
the tank I similarly to the tubs 3a, 3b, 3c, 3d, 3e,
tracting sections. In the former speci?c con
3]‘, So, 3h, 32', 37' and each having a hub II from
struction, these paddle Wheels, all driven from a
which extend the same number of curved, per
common drive shaft, are all arranged with their
forated blades I9 all spaced apart equiangularly
respective blades set on like centers. That is to
on their respective hubs. The hubs ll are se
say, each paddle wheel has the same number of
cured to rotary shafts 2| each of which has ?xed
blades spaced apart equi-angularly about the
axis of rotation, and the corresponding blades
all having the same angular relation to a ref
erence plane (for example, a vertical plane ex
thereto outside of the tank I a worm wheel 23
in mesh with a worm 25 on a main driving shaft
2i‘ which receives power from a suitable source
tending across the apparatus through the axis Of 75 (not shown).
2,405,105
5
The paddle wheels 4a, 4b, 4c, 4d, 4e, 4]‘, 4g, 4h,
42‘, 47' rotate relative to their respective tubs at
each station and, in so doing, feed the solid ma
terial in each tub toward and into the next suc
ceeding tub. The solid material 1 may be sup
plied to the tank by a suitable conveyor, such as
a screw conveyor 29, and is introduced into the
tank at the ?rst extraction station or section 317
through one or more delivery spouts 3|. Where
6
tion in succession. After passing through the
strainer H in section 3a the liquid solvent flows
into a tank 31 from which it is withdrawn
through a pipe 39 which extends down nearly
to the bottom of the tank 31 to insure drawing
off any sediment or sludge which may tend to
collect in the compartment 31. The pipe 38 also
insures a proper level being maintained for the
liquid 9 in the tank, this level being dependent
the tank I is fairly wide, two spouts may be used, 10 upon such factors as the nature of the material
handled, the extractive effect desired, the rate
as shown in Figure 3, in order to obtain even
distribution of the material 1 across the width
' of ?ow of solvent, etc., but in any case being pref
erably slightly above the meeting edges 5 be
of the tank. If desired, the spout which is fed
?rst by the conveyor 29 may be provided with
a sliding gate or valve 32 which may be ad
tween adjacent tubs. The spray pipe 35 is lo
15 cated above the level of the solvent 9, as can be
justed-to insure substantially equal ?ow of the
solid material through each of the spouts 3|. In
any case, the solid material introduced into the
clearly seen from Figure 1. With this arrange
ment, the fresh solvent discharged through the
pipe 35 comes in contact with the solid residue
on the conveyor :33 after the residue has been
station or section 3b is fed therethrough in seg
regated masses to the next station 30 by the 20 raised above the level of the liquid and partially
drained. By thus intimately spraying the resi
blades of the associated paddle wheel 4b. At
due with fresh solvent, a very de?nite additional
the station 3c, the blades of the paddle wheel
extractive effect is obtained and a higher extrac
40 pick up these segregated masses of solid ma
tive efficiency is realized.
terial and feed them through the tub 30 to the
The solid material introduced into the extrac
tub 3d where the paddle wheel 4d picks up these 25
tor through the spouts 3| may include many
masses, in turn, and so on until, ?nally, the last
?ne particles which, in the dry or substantially
paddle wheel 47' advances the leached material
dry state, float on the surface of the liquid sol
out of the tub 3i and onto a suitable conveyor,
vent 9. With the particular construction shown
such as a drag conveyor 33, which passes out of
the tank in an upwardly inclined direction to dis 30 in my prior patent, these ?ne particles'were car
ried away by the ?owing liquid without being
charge the leached residue.
properly extracted. To intercept these ?ne par
If the paddle wheels were all set on the same
ticles, vthere is now provided the additional “?lter
center on their respective shafts 2|, it is obvious
section” 3a between which and the ?rst extrac
that corresponding blades of each paddle wheel
tion section 31) is pivotally mounted, as by means
would encounter the loads provided by each seg
of several hingestraps 40, a baffle plate 4| which
regated mass of material 1 in each tub at the
extends across the entire width of the tank I
same time, as in the apparatus of my above-iden
and is preferably provided with rubber or other
ti?ed patent. This would result in periodic and
suitable wipers 43 along its side edges, as clearly
considerable surges in power requirements and
shown in Figure 3. The baffle plate 4| is piv
would impair the extractive e?iciency. To avoid
otally carried on a vrod or shaft 45 which is lo
this, each paddle wheel is so mounted on its shaft
cated above and slightly to the left of the meet
i2| that‘its blades are spaced a suitable angle, for‘
ing edge 5 between the tubs 3a and 3b, as viewed
example 10°, from the corresponding blades of
in Figs. 1 and 2, or above the tub 3a, the lower
the next adjacent paddle wheel, the settings be
ing progressive. Thus, for example, with the 45 end of the baffle plate being bent at an angle to
provide a flange -4|a which‘ extends into the tub
paddle wheel 4b in place, the wheel 40 is so set
32) below the level of the liquid 9. By locating
that its blades are displaced 10° counter-clock
the pivot shaft 45 as above described, the baffle
wise on its shaft relative to the blades of the
plate 4| tends constantly to swing down in a
wheel 41); the paddle wheel 411 is so set that its
50 clock-wise direction, as shown, to bring its ?ange
blades are displaced 20° counter-clockwise on its
4|a down against the adjacent meeting edge 5.
shaft relative to the blades of the wheel 41) but
A plurality of spacing blocks 41 which are se
only 10° relative to the blades of the wheel 40;
cured at spaced intervals to the lower face of
the paddle wheel 4c is so set that its blades are
the flange 4|a serve to keep the flange 4|a
displaced 30° counter-clockwise on its shaft rela
tive to the blades of the wheel 4b, only 20° rela 55 spaced su?iciently from the edge 5 to permit the
liquid 9 to flow from the tub 3b to the tub 3a.
tive to the blades of the wheel 40, and only 10°
Secured to the ba?le plate 4|, as by means of
relative to the blades of the wheel 4d, and so
several spaced straps 48, and extending into the
on. In this way, substantially uniform power
requirements are maintained and more uniform
?lter section or station 3a. in the path of move
I through a perforated spray pipe 35 which ex
tends across the width of the tank between the
upper and lower strands of the conveyor 33 and
is arranged to direct its spray downwardly onto 65
the width of the tank. The scraper 49 is arranged
to cooperate with each blade I9 of the paddle
60 ment of the blades of its paddle wheel 4a is a
extraction is obtained.
scraper 45 which also extends substantially across
The ?uid solvent -9 is introduced into the tank
wheel 4a, the engagement of each blade there
with serving to swing the baiflc.plate counter
clockwise and away from the adjacent meet
ing edge 5 to expose a relatively large opening
therebetween through which may be passed solid
strand of the conveyor, as clearly seen from Fig
material scraped off from each of the blades
ure 1. The tank is preferably given a slight fall
from the tub 37' to the tub 3a wherefore the sol 70 in turn.
When the extractor is set up for operation, the
vent 9 will flow, by gravity, toward the tub 3a
tubs
3a. 3b. 3c, 3d, 36, 3f,
3h, 32‘, 37' are ?lled
and in a direction opposite to that in which the
to the desired level with a suitable solvent and the
solid material '| is advanced from the tub 3b to
particles of solid material are introduced through
the conveyor 33, the solvent becoming more and
more concentrated as it passes through each sta 75 the spouts 3| into the ?rst extraction section 3b.
the solid residue which is being carried upward
ly by the ?ights 34 secured to the then lower
2,405,105
8
The rotating blades l8 of the paddle wheel 4b
butter from cocoa bean residue.
Other appli
_ divide the fallingmaterial into segregated masses
cations will, no doubt, readily suggest themselves
and carry these masses down into the solvent 9
then at the station 3b where the material is
to those skilled in the art. Also, various changes
in and modi?cations of the particular form of
thoroughly wetted and some of the soluble con
the invention disclosed herein, as well as other
stituent extracted therefrom. The material is
then advanced to the second extraction station
30 where further extraction takes place, and
thence successively through each of the extrac
embodiments thereof, all falling within the spirit
of the present invention, will undoubtedly sug
they then tend to agglomerate and remain with
other unit. "‘
gest themselves, -I therefore desire that my in
vention shall not be limited except insofar as is
tion stations 3d, 36, 31‘, 3g, 3h, 3i, 37‘ ‘against the 10 made necessary bythe prior art and by the spirit
of the appended claims.
?ow of fluid which has a smaller concentration of
I claim as my invention:
soluble constituent at each station as the ?nal
1. In countercurrent leaching apparatus in
extraction station 37' is approached. The solvent
which solids to be leached are introduced adja—
meanwhile ?ows from the conveyor 33 toward the
tank 37' from which it is withdrawn as heretofore 15 cent one end of the apparatus and solvent liquid
adjacent the other, a pair of adjacent leaching
described.
units having a common top edge constructed to
Of the solid material fed through the spouts 3|,
permit the flow of solvent successively through
many particles are so ?ne and light that they
said units, means for introducing into one of
float on the surface of the liquid 9 and even tend
to ?oat in the air above the tub 3b, particularly 20 said units constituting a receiving unit the solids
to be leached, and a barrier supported above and
if they bounce back off from the blades IS. The
in proximity to said common top edge for yield
wipers 43 and a ?xed plate 5| secured to the top
ing movement toward said receiving unit, said
2 of the tank between the spouts 3| and the swing
barrier being located to normally prevent pas
ing ba?le plate 4| keep the ?ne dust from passing
directly into the ?lter section 3a and from clog 25 sage of aggregated solids from said receiving unit
over said common top edge and into the other of
ging the hinges of the baille plate 4|. These ?ne
said units, and said barrier being yieldable to
particles eventually reach the surface of the liquid
ward said receiving unit to permit reverse pas
9 in the tub 3b and are carried thereby under the
sage over said common top edge back to said
flange Ma. The. particles are thus immersed in
the liquid and become thoroughly wetted, and 30 receiving unit of any solids that may reach said
the mass of solid material.
However, some of
these particles are carried by the flowing liquid
into the section 3a where the proportion of liquid
to solid is far greater than in the extraction sec
tions 3b, 3c, 3d, 3e, 3}, 39, 3h, 31', 31‘. Consequently,
ample opportunity is afforded for these particles
to become thoroughly saturated with the solvent
and to settle out in the form of sludge. If any of
these particles do not settle out, they are inter
cepted by the blades of the rotating paddle Wheel
4a or, if they pass through the perforations of
the blades, they are intercepted by the strainer | |.
As the paddle wheel 4a turns, the outer edges
of its blades scrape the particles from the surface
of the strainer | | and also push forward the other
particles which have settled in the bottom of the
?lter section 3a, the agglomerated particles cling
ing to the blades |9. Eventually, the middle por
tion of each curved blade l9 ?rst comes in con
2. In countercurrent leaching apparatus in
which solids to be leached are introduced adja
cent one end of the apparatus and solvent liquid
adjacent the other, a pair of adjacent leaching
units having a common top edge constructed to
permit the flow of solvent successively through
said units in one direction, rotating means in
each unit arranged to submerge the solids there
in and to advance said solids therefrom in the
reverse direction,” means for introducing into the
?rst of said units considered in said one direc
tion and constituting a receiving unit the solids
to be leached, and a barrier supported above
and in proximity to said top edge for yielding
movement toward said neceiving unit, said barrier
being located to normally prevent passage of
aggregated solids over said common top edge from
said receiving unit to the other of said units, and
said barrier being yieldable toward said receiving
unit to permit passage in said reverse direction
tact with the scraper 49 and continued rotation
from said other unit back to said receiving unit
of the paddle wheel causes the baffle plate 4| to
of any solids that may reach said other unit and
be swung away from the adjacent meeting» edge
that are advanced over said common top edge
5 to expose a large opening into the tub 3b. At
the same time, since the blades l9 are dragged 55 by the rotating means in said other unit.
3. In countercurrent leaching apparatus in
against the scraper 19, the scraper removes the
which solids to be leached are introduced adja
sludge from the blades and causes it to be de
cent one end of the apparatus and solvent liquid
posited in the tub 3b through the temporarily
adjacent the other, a series of successive leach
exposed opening. Thus, the ?ne particles join the
mass of material and none of the material is lost. 60 ing units adjacent ones of which have a common
To permit the ba?le plate to swing properly
between the blades of the two paddle wheels in the
top edge constructed to permit the ?ow of solvent
in one direction through and over the series,
rotating means in each unit arranged to sub
merge the solids therein and to advance said
blades become fouled, these two wheels are suit
ably displaced. A diiference of approximately 65 solids successively from unit to unit over said
common top edges in the reverse direction, means
50° in the setting of the blades on their respec
for introducing into one of said units adjacent
tive shafts 2| has been found quite satisfactory.
the solvent discharge end of the apparatus and
From the foregoing description, it will be ap
constituting a receiving unit the solids to be
parent that I have provided an improved leaching
apparatus by means of which soluble constituents 70 leached, there being an additional unit follow
ing said receiving unit in the direction of flow
may be extracted with great ef?ciency from solid
of said solvent and prior to the discharge of
particles of event the most minute size. One
said solvent, and a barrier supported above and
application of the improved apparatus herein de
in proximity to the common top edge between
scribed wherein it has proven particularly ad
vantageous is in the solvent extraction of cocoa 75 said receiving unit and said additional unit for
sections or stations 3a and 3b without having the
2,405,105
yielding movement toward said receiving unit,
said barrier being located to normally prevent
passage of aggregated solids over said last men
tioned top edge from said receiving unit to said
additional unit, and said barrier being yieldable
toward said receiving unit to permit passage in
said reverse direction from said additional unit
back to said receiving unit of any solids that may
reach said additional unit and that are advanced
over said last mentioned top edge by the rotat
ing means in said additional unit.
ll. Leaching apparatus according to claim 3
wherein said barrier comprises a baflle plate
mounted above said additional unit and extend
ing down into said receiving unit below said com
mon top edge therebetween, and wherein means
10
and said scraper being adapted, while engaging
each of said blades in turn, to scrape off from
each blade the material advanced thereby and to
effect deposit of said advanced material in said
other tub through said enlarged opening.
8. In the method of extracting from a mate—
rial a soluble constituent therein by means of a
?owing liquid solvent for said constituent ar
ranged to ?ow successively through a plurality
of extracting units, said material including
particles of such ?ne form that said particles
tend to ?ow on the surface of said liquid when
deposited thereon in the dry state and to be
carried along by said ?owing liquid, the steps
5 which comprise introducing said material includ
ing said fine particles to said liquid at one of
said units constituting a receiving unit, causing
the relatively heavier particles of said introduced
are provided for normally maintaining said ba?le
plate in slightly spaced relation to said last men
material to be immersed and agglomerated in
tioned common top edge.
5. Leaching apparatus according to claim 3 20 the liquid at said receiving unit, screening said
agglomerated heavier particles against passage
characterized in that said liquid is maintained
at substantially a, predetermined level at said
from said receiving unit into the next succeeding
unit following said receiving unit in the direc
leaching units, characterized further by the ad
dition of a drag conveyor for removing to a point
tion of ?ow of said liquid while permitting said
above said level the solid residue advanced from 25 ?owing liquid to advance said ?ne particles to
said next succeeding unit, causng said advanced
the last of said units considered in said reverse
?ne particles to become immersed in said liquid
direction, and characterized still further by the
at said next succeeding unit whereby to effect
addition of means for spraying fresh liquid onto
thorough wetting and agglomeration of said
said removed residue at said point.
6. In leaching apparatus for extracting a 30 advanced fine particles, and thereafter e?ecting
return of said agglomerated ?ne particles from
soluble constituent from solid material by means
said next succeeding unit back to said receiving
of a ?uid solvent, the combination of a pair of
unit for immersion thereof in the liquid solvent
adjacent tubs adapted to contain both said ?uid
then at said receiving unit.
and said solid material, a rotatable paddle wheel
9. In the method of extracting from a mate
associated with one of said tubs and having a 35
plurality of blades adapted, during rotation of
rial soluble constituent therein by means of a
?owing liquid solvent for said constituent ar
said paddle wheel, to advance the solid mate
ranged to ?ow in one direction successively
rial in its associated tub toward the other of ‘said
through a plurality of extracting units, said
tubs, and means associated with said paddle
material including particles of such ?ne form
wheel for removing from said blades all of said
material advanced thereby and for effecting de
that said particles tend to ?ow on the surface of
said liquid when deposited thereon in the dry
posit of said advanced material in said other tub,
said removing means comprising a pivotally
state and to be carried along by said ?owing
mounted member normally occupying a position
liquid, the steps which comprise introducing said
in the path of movement of and adapted to be 45 material including asid ?ne particles to said
successively engaged by each of said blades dur
liquid at an intermediate one of said units con
ing rotation of said paddle wheel, the engagement
stituting a receiving unit, causing the relatively
of said member by said blades causing said mem
heavier particles of said introduced material to
ber to swing on its pivotal axis while maintain
be immersed and agglomerated in the liquid at
ing engagement with each blade in succession
said receiving unit, screening said agglomerated
to thereby remove the solid material from each
heavier particles against passage from said re
blade during swinging movement thereof.
ceiving unit into the next succeeding unit fol
7. In leaching apparatus for extracting a
lowing said receiving unit in the direction of
soluble constituent from solid material by means
?ow of said liquid while permitting said ?owing
of a ?uid solvent, the combination of a pair of 55 liquid to advance said ?ne particles to said next
adjacent tubs having a common meeting edge
succeeding unit, causing said advanced ?ne parti
and adapted to contain both said ?uid and said
cles to become immersed in said liquid at said
solid material, a rotatable paddle wheel asso
next succeeding unit whereby to effect thorough
ciated with one of said tubs and having a plu
wetting and agglomeration of said advanced ?ne
rality of blades adapted, during rotation of said
particles, thereafter effecting return of said ag
paddle wheel, to advance the solid material in its
glomerated ?ne particles from said next succeed
associated tub toward the other of said tubs, a
ing unit back to said receiving unit for immersion
ba?le plate pivotally mounted above said meeting
thereof in the liquid solvent then at said receiving
edge and arranged to swing toward said edge,
unit, and ?nally advancing said returned, ag
means normally maintaining said baille plate 65 glomerated ?ne particles successively through
spaced slightly from said edge whereby said ?uid
each of the remaining units in counter-current
may pass from said other tub to said ?rst named
relation to the flow of said liquid and immersing
tub, and a scraper carried by said ba?ie plate
said agglomerated ?ne particles at each succeed
and extending into the path of movement of said
ing one of said remaining units in the liquid
blades, said blades being adapted to successively 70 instantaneously in each of said last mentioned
engage said scraper to swing said baille plate
succeeding units.
away from said edge and thereby expose a larger
ANGUS B. KENNEDY.
opening between said edge and said bal?e plate,